Conventionally, there is a technique to provide an electrode tip made of a noble metal at a ground electrode of a spark plug (see International Publication No. WO 2012/167972). In this conventional technique, the electrode tip is welded to an electrode base material forming the ground electrode. That is, the electrode tip is joined to the electrode base material via a melt portion which is formed by a portion of the electrode tip and a portion of the electrode base material being melted in welding.